1. Technical Field
The present invention relates to a timepiece.
2. Background Technology
One well-known wristwatch is provided with a case forming a ring shape, and a back cover mounted onto a back side of the case (for example, see Patent Citation 1). With the wristwatch recited in Patent Citation 1, the back cover is fixed to the case via a bolt (screw). When the wristwatch is produced in this manner, a bolt must be used to screw the back cover and the case together, and a problem is presented in that this production work is laborious and in that the bolt can loosen during the work.
Further, with the wristwatch as set forth in Patent Citation 1, a metal material or ceramic is used as a constituent material of the case. In a case where a metal material is used as the constituent material, an internal screw thread into which an external screw thread of the bolt is screwed can be formed directly on the case, but forming the internal screw thread on the case is difficult in a case where a ceramic is used. For this reason, a metal tube in which a internal screw thread has been formed on an inner peripheral part is embedded in the case, and the internal screw thread of this metal tube and the external screw thread of the bolt are screwed together. When the metal tube of such description is used, problems in terms of production are presented in that the number of parts is thereby increased, there is the additional step of embedding the metal tube, and the like.
Also, with the wristwatch recited in Patent Citation 1, as described previously, the back cover is fixed to the case via the bolt. This bolt is locked in toward the back cover from the outside of the case. For this reason, a head part of the bolt (a screw head) is exposed, and a problem is presented for the wristwatch in that the aesthetic appearance is adversely affected.    Japanese Laid-open Patent Application No. 2010-127765 (Patent Document 1) is an example of the related art.